Tilt belt grinder



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United States Patent TILT BELT GRIN DER Archibald M. Urquhart, ElSegundo, Calif., assignor of one-half to Sierra Machinery Co., Inc.,Reno, Nev., a corporation Application June 15, 1953, Serial No. 361,605

16 Claims. (Cl. 51-142) This invention relates to grinders for abrasiveaction on work pieces and more particularly refers to an apparatus thatincorporates an abrasive belt to carry out the grinding operation. Theinvention contemplates the pro vision of a work supporting surface tosupport work pieces and the further provision of means to vary the angleof the abrasive belt relative to the work surface.

One problem in the construction of a grinding apparatus of this generalcharacter is to prevent excessive heating of the work pieces and of theapparatus itself by the friction involved in the abrasive action on thework pieces. This problem is solved in part by using an abrasive beltwhich by its motion tends to dissipate generated heat. A feature of thepreferred practice of the invention, however, is that this problem iscompletely solved by a cooling system to absorb heat from-the worksupporting surface in the region of the traveling belt. Preferably thecooling system is a refrigeration system having an evaporator unitadjacent the work supporting surface of the apparatus.

A second problem is to provide an arrangement for supporting the runningbelt at various angles relative to the work supporting Surface in suchmanner as to facilitate precision in the grinding of work pieces. Inthis regard a feature of the invention is the concept of using a tiltstructure on which the belt is mounted and which rotates about an axislocated substantially at the line of intersection of the abrasivesurface of the belt with the plane of the work supporting surface. lnthe preferred practice of the invention the work surface terminates in arelatively sharp straight edge substantially at this line ofintersection and the tilt structure carries an arcuate scaleintersecting the plane of the work supporting surface to indicate theangle of the traveling belt relative to the work supporting surface.

A third problem is to pivotally mount the tilt structure in such manneras to facilitate replacement of the abrasive belt when required. Thesolution afforded herein is to pivotally support the tilt structure fromone side only, the other side being clear to permit a belt to beinstalled or removed with maximum convenience and minimum delay.Preferably means is included to keep the belt normally under tension anda feature of certain practices of the invention is the provision ofquickly operable means to release such tension thereby to facilitate theremoval of one belt and the installation of a replacement belt.

A fourth problem is to keep the pivotal mounting means for the tiltstructure below the plane of the work supporting surface at all anglesof the tilt structure, thereby to avoid interference with work pieces onthe work supporting surface along the axis of rotation of the tiltStructure. In this regard, the invention is characterized by the use ofa trunnion on the tilt structure and a cooperating stationary bearingmember, both of which members have the cross sectional configuration ofa segment of a circle of an arcuate extent of less than half of thecircle. By virtue of this semi-circular configuration, the axis of thebearing may be in the plane of the work supporting surface with all ofthe structure of the bearing below the plane. A feature of the bearingarrangement in the preferred practice ofthe invention is the provisionof cooperating arcuate shoulders on the two members to preventseparationv of the trunnion member from the bearing member.

A iifth problem is to adapt such an apparatus for the rapid grinding ofwork pieces on which the desired ground surfaces of thework pieceprogressively change in angle along the work piece. To process such awork piece the angle of the tilt structure must be progressively changedas the work piece is progressively shifted on the work supportingsurface relative to the abrasive belt. For accurate grinding, both ofthe operators hands are required to hold the work piece in position,neither hand being free to change the angle of the tilt structure. Theproblem is met, iirst, by providing power means to vary the rotaryposition of the tilt structure and, second by providing remote controlmeans operable by movement of the operators leg to change the tilt angleby small increments as the operator manipulates the work piece relativeto the abrasive belt. The power means is, of course, reversible andpreferably is adapted to be set in advance to operate in either of thetwo opposite directions of tilt change. The preferred practice of theinvention is further characterized by the inclusion of automatic meansto releasably hold the tilt structure at any angle to which it may beadjusted.

A sixth problem is to prevent the accumulation on the work supportingsurface of particles released by the abrasive action and to keep suchparticles from being released into the atmosphere. In this regard, thepreferred practice of the invention is further characterized by the useof a blower system to remove the particles, the blower system includinga shroud on the tilt structure enclosing the traveling belt.

The features and advantages of the invention entering into the solutionof these various problems may be understood from the following detaileddescription of preferred embodiments of the apparatus considered inconjunction with the accompanying drawings.

In the drawings, which are to be regarded as merely illustrative:

Figure 1 is a side elevation of one embodiment of the invention withparts broken away to reveal Yconcealed structure;

Figure 2 is a front elevation of the same embodiment of the inventionwith parts broken away and other parts shown in section;

Figure 3 is a fragmentary sectional view'to indicate the manner in whichthe angle of the traveling belt changes relative to the work surfacewhen the tilt structure is rotated to various positions;

Figure 4 is a fragmentary section taken as indicated by the line 4 4 ofFigure 3;

Figure 5 is an exploded perspective View of the essential parts of thestructure for pivotally supporting the tilt structure;

Figure 6 is an enlarged fragmentary section taken as indicated by theline 6 6 of Figure l;

Figure 7 is a diagram illustrating the arrangement for controlling theangle of the tilt structure in the first embodiment of the invention;

Figure 8 is a View partly in side elevation and partly in sectionshowing a second embodiment vof the invention;

Figure 9 is a detail, partly in section and partly in side elevation,showing the structure in the region in which the traveling beltintersects the plane of the work supportingv surface in the secondembodiment of the invention;

yFigure l0 is a view of the second embodiment of Patented Nov. 29, 19.55

3; the` invention, partly in front elevation and. partly in4 section;

Figure l1 is a plan view of the second embodiment ofv the. inventionywithparts.y broken away, and:

Figure 12 is, an enlargedv fragmentary section of the bearing structurefor the. tilt structure in the second embodiment of the. invention.

The working parts of the iirst embodiment ofthe invention illustrated byFigures l to 7 are carried: in.l part byA a Xed base structure,ydesignated as.` a whole by: nurneral 2l),k and. inV part byr atiltstructure, designated as a, whole. bynumeral 21'. These twoAstructures make take various forms in various practices of theinvention.

The base structure 20 has the. general character of a work table and hasa horizontal;` work supporting surface 22', which workvsupporting'surface is provided by aplurality of: top plates 23 lying ina common plane. The basestructure includes upright angle members 27 atthe fourcorners which are interconnected by frame elements includingupper horizontal angles 28 andk lower horizontal angles 29. Preferablythis frame structure isv supported by four adjustable legsy at the fourcorners, each. of which legs comprises a foot pad 3,0 on an. adjustablescrewl 31. Preferably the framework of the base structure 20. isI closedon all sides by a heavy sheet metalV housing 32 that is suitably'attached to the framework.

The tilt structure 21 carries an endless abrasive belt` Bvand causes thebelt to travel in a` straight run or operating path 36` at the frontofthe tilt structure with theabrasive surface 37 of the belt facingforward as shown in Figure 2. Preferably theworksupporting surface ofthe base structure 2.0 provided by the plates 23 terminates closelyadjacent to the forward abrasive surface 37' of the belt B andpreferably the plate material is beveled' to form-a relatively sharpedge 33. It is contemplated that the tiltstructure 21 willl be mountedon the base structure 20 to rotate about an axis in the region of theintersection of the operating run or path 26 ofthe belt and the plane ofthe work surfaceI 22 of theA basel structure. In they preferredpractices of the invention as exemplifiedl by the present embodiment,the aXis'- of rotation of the tilt structure 21 substantially coincideswith the intersection of-I the abrasive surf-ace 37' offthe belt andythe plane of' the work supporting surface 22, and the beveled edge 38,which is in that plane, is substantially atfthis intersection. Thus, ineffect, rotation-of V the tilt structure 21 rotates the abrasivelsurface 37 of the belt about the beveled edge 38.

Preferably a suitable scale orindex means is providedV to indicate theangle of adjustment" of the-tilt structure. form`A ofl an arcuate bar-39# concentric to the axisof rotation.` The bar 39,I as best shown inrFigures l and 2, isV mounted onV the side of the tlt structure byvsuitable brackets 40, and the top ofthe base structure 20- is aperturedto clear the bar. The bar 39may bel marked with a graduated scale 41(Figure 2) to'be readv with reference to the work supportingsurface 22,the scale beingcalibrated in terms ofdegrees of rotation.

As heretofore stated, it is further contemplated' that a cooling systemwill be provided in the preferred practices of the invention toabsorbheat created by the abrasive action of the belt B- on work pieces. AnyYsuitable-cooling system may be employedfor this purpose; In the presentembodiment ofthe invention', thecooling system is a refrigeration systemwhich includes an evaporator or cooling unit 44 best'shown -in Figures 3'and 4. The unit comprises a series of coils 45 which extend from amanifold 46 to two-plate member 47, the twoplate memberformingtheportion of the work surface 22 in the region immediately in front of thebelt B. The two-plate member 47 is provided with uid passages in theform of bores48 to receive the refrigerant from the coils 45' and thesepassages are connected by corre- Such a scale may, for example, be inthecooling unit is connected to the usual condenser 58` (Figure 1').

The tilt structure 21 includes a heavy side plate 60 which servesnotonly' as: aframe memberk tosupport the various parts, but also servesas. one. side of a shroud. The shroud encloses the belt B on all sidesand is provided with a window 61 to expose the operating run of the beltin the region of the beveled edge 38. The shroudstructure includes a;wallV member 62' thatv extends. fromlthe lower edge. of the window 6:1-aroundlther front, bottom, back and top. of the tilt structure andalsoincludesa side wall member 63 opposite from. the heavy side plate60. This.` side wall: member 63' is. removable and@ isnormally held. inpositionA by. suitable releasable fastening means; As shownin Figure-2,the fastening'means may comprise screws 641pivotallly mounted onbrackets 65y on the removable wall member 63',

which. screws carry Wing' nuts 66Y toy engage slotted clipsy` 67l ontherpermanentwall memberV 62. A.- feature of this embodiment of theinvention is thatthis-side-.of the tiltstructure 21'.` is clearandiunencumbered so. that it is merely necessary to-loosen theA wingnuts: 66 andf` remove the sidewall member 63 to make the entireinteriorofthe tilt` structure accessiblezfor quick removal andP replacementVofthe abrasive beltlB-.

The--belt- B is looped around an upper idler drum` or pulley 7 Gand a`lower' driven-drum orl pulley 7-1, andl pref#v erably the operating run36 of the belt is backed by suit-A able structuresuchas a-backingplate=72- (Figures `1 and 3) that isiixedlymeunted'on the heavy-'sideplate 601 inside-the shroud.V The upperpulley` fismounted-by suit#ablebearings73 on a spindle 74'lthat is; integral! with a` baseplate-75.- Thebase plate 75 'thatl carries 4they .spindle`r ismounted byscrews76on-'aslide assembly that is-mov-` able` in" an* upright slot 77Vin the hea-vyside plate 60-z This slideassemblytincludes'an-inner pla-teSillon the inner side of-theslot and' an outer slide member 81"whichfisyconnected tothe-'inner plate" byI afb-lock 821' inthe; slot 77'.Theouter'slide memberlis guided-bytwofslide railsI 83 and84 that` aremounted onV the outer side of the heavyside plater 60 by suitable-screws815i TheV outer slide-member 81I may be controlledby a screw 86 havingan operating handle 87, and for this purpose the/slidemember S1.is'formed withan earl-'SSAthat isthreadedfor engagement bythe screw.Preferably:l al locknut-89His' mountedlon the lowerendt-of-` the screw.'The screw -86 -is-freely'rot-atable-in -an ear 90'onthe heavy side platey60- and is ofy enlarged-"diameter atits upperv end as indicated at'9-1* for1l engagement4 withA the upper side offtheftear. Preferably,aclamping screw 92havingan operatingknob; asshown, isv mountedfintheouter slide' member 63 for -retractible engagement withfthe heavysideplate-6U:l Thtis1 screw 92 serves to releasably'rretain the slideassemblyin adjusted positionasa further precautionagainst looseningofthe b'elt B. It isfapparent-thatthis arrangement for varying thespacingof the upper pulley 7 0 from `the 'lowerpu'lley- 71lpermitscorrespondingvaria-v tiorr in--the dimensions of-'belts used with the'apparatus and ymakes it possible to placel a belt underIwhatever'tension mayi-be'desired:

The-lowerdrive' pulleyqlrnay be mountedA on a-shaft 96 that isjournaled` bysuitable bearings 97fin a cylindrical bearing memberS: Thebearing member 98 "extends" througl'lthe heavy side plate 60andiisattach'edithereto by suitablev screws 99." The outer end of' theshaft'9`6'l carries a sheave I00whi `:h is operatively' connected'by awere.

multiple V-belt 101 with a drive sheave 102. The drive sheave 102 ismounted on the shaft 1030i a suitable motor 104. As best shown in Figure1, the motor 104 is mounted by screws 105 on a base casting 106 and thebase casting 106 is, in turn, mounted `on'the outside of the tiltstructure shroud by suitable screws 107.

The tilt structure 21 may be pivotally mounted on the base structure 20in various ways in various practices of the invention. In this instance,the tilt structure is pivotally supported entirely from one side so thatthe opposite side may be free and unencumbered to permit quickreplacement of a belt in the manner heretofore described. A feature ofthe illustrated construction is the manner in which the tilt structureis mounted for rotation about the beveled edge 38 as an axis without anyportion of the pivotal mounting structure extending above the plane ofthe work supporting surface 22. Such an arrangement permits full freedomfor use of the work surface 22 on both sides of the tilt structure 21,as well as in front of the tilt structure.

In the present construction, the tilt structure 21 is supported entirelyby a single journal body or trunnion member 112 which is rigidly mountedonv the heavy side plate 60 of the tilt structure. It is contemplatedthat the trunnion member will have the cross-sectional configuration ofa segment of a circle having an arcuate extent of less than 180, thesegment beingtruncated to space the trunnion member radially away fromthe pivot axis along the beveled edge 38. It is further contemplatedthat the trunnion member 112 will be journaled by at least one bearingmember that is also segmental in cross sectional configuration and hasan arcuate extent of not more than approximately 180. It is apparentthat with such a segmental trunnion member mounted in a segmentalbearing member, both members may be positioned below the plane of thework supporting surface 22, without the trunnion member rocking into theplane of the work supporting surface throughout the required range ofpivotal movement of the tilt structure 21. Since both the trunnionmember and the associated bearing member lie below the horizontal planeof the axis of rotation of the tilt structure, the problem presentsitself of maintaining the trunnion member in seated engagement with thebearing member. For this purpose, the two members are provided withmutually engaging arcuate shoulders and for this purpose preferably oneof the members is formed with an arcuate groove to receive an arcuateange of the other member. Various specific constructions may be employedto carry out this concept.

In the present embodiment of the invention, as may be seen in Figure 2,the trunnion member 112 is journaled in an inner bearing member 113close to the tilt structure 21 and in an outer bearing member 114 closeto the side of the base structure 20. As best shown in Figure 5, thetrunnion member 112 is formed with two arcuate ribs 115 corresponding tothe two bearing members 113 and 114 and each of these ribs is grooved toform a pair of arcuate peripheral flanges 116. Each of the two bearingmembers 113 and 114 is of split construction, being formed of separablesections 117. Each pair of the separable sections 117 forms an arcuategroove 118 to receive the corresponding rib 115 of the trunnion memberand the groove 118 is formed with overhanging arcuate walls or flangesto engage the rib anges 116. Thus, the rib anges 116 and the overhangingwalls or anges 120 of the bearing members constitute arcuate shouldersin mutual engagement to maintain the trunnion member 112 seated in thetwo bearing members 113 and 114. The separable section 117 of eachbearing member are held together by suitable screws and each of thesections is attached to the underside of one of the top plates 23 bysuitable bolts 121.

If desired, means in addition to the trunnion 112 and the two bearings113 and 114 may be provided to guide and support the tilt structure 21in its movement about its axis of rotation. For this purpose, guidemeans in the form of a heavy upright plate may be mounted inside thebase structure 21 and supported by a heavy horizontal frame member 126.The upright plate 125 is provided with an arcuate slot'127 concentric tothe axis of rotationy to receive a pair of rollers 128 carried by thetilt structure. As shown in Figure 6, the two rollers 128 are mounted onspindles 129 carried by a block 130 and the block 130 is attached toears 131 that are iixedly mounted on the heavy side plate 60 of the tiltstructure. In the construction shown, the block V130 is secured bysuitable screws 132 that extend through ,the ears131 and through shims133 into threaded engagement with the block.

Preferably additional rguide rolls carried by the tilt structure engagethe opposite sides of the upright plate'125. For this purpose suitablerollers may be mounted on brackets or arms extending from the previouslymentioned bearing member 98 on opposite sides of the upright plate 125.Figure 1 shows one such arm or bracket 134 carrying a guide roller 135in rolling contact with the outer surface of the upright plate 125.

Any suitable means may be provided for locking the tilt structure 21 tovarious angles of tilt about its axis of rotation but preferablysuitable power means is utilized under remote control and preferably thearrangement permits control to be exercised by movement of the operatorsleg s'o that he may change the angle of tilt of the traveling belt Bwithout taking his hands off a work piece on the work supporting surface22. Inv the present embodiment of the invention, for example, thedirection in which the power means operates to change the inclination ofthe tilt structure 21 is determined in advance by a pair of footswitches located at the front of the machine at positions convenient forthe operator. Energization of the power means to rotate the tiltstructure is controlled by` what may be termed a knee switch 141 whichis mounted on the front of the base structure in a position to beactuated by the operators knee. I

In the construction shown in the drawings, an operating arm 142 that isattached to the outer end of the trunnion 112 by suitable screws 143, isactuated by compressed air supplied to a power cylinder 144. The powercylinder 144 houses the usual piston (not shown) which is connected tothe operating arm 142 by a piston rod 14S that terminates in a clevis146. The power cylinder 144 is pivotally mounted at its rear end to afixed bracket 147 by a suitable pin 148 to rock Vertically as requiredto follow the arcuate movement of the operating arm 142.

The operating arm 142 of the tilt structure is connerted in similarmanner to a hydraulic cylinder 150 which is pivotally mounted on asecond bracket 151 by a suitable pin 152. The hydraulic cylinder 150also houses a piston (not shown) which is connected to the operating arm142 by a piston rod 155 that terminates in a clevis 156. The manner inwhich the power cylinder 144 and the hydraulic cylinder 150 cooperatefor control of the angle of inclination of the tilt structure 21 may beunderstood by reference to the diagram in Figure 7.

The two ends of the hydraulic cylinder 150, which cylinder may contain asuitable oil, are interconnected by a by-pass tube through which theliquid ows under the control of a by-pas's valve 161 and a meteringvalve 162. The by-pass valve 161 is normally closed to block by-pass owand thus lock the operating arm 142 in any position to which the arm maybe adjusted. The by-pass valve 161 is a solenoid valve controlled by theknee switch 141, the valve being normally closed and the knee switchbeing normally open.

The oppositeends of the power cylinder 144 are connected by pipes 164and 165 respectively with opposite ports of a 4-way control valve 166. Athird port of the control valve 166 is connected by a pipe 167 to apressure regulator 168 (Figure 1), which regulator is avifauna in turnconnected to va suitable source of compressed air (not shown).Preferably the supplygline Ithi"o11` gh the pressure regulator16Spr'ovided with afsutable vtrap 1'69 for the removal 'of water anddirt and 1is -also p'r'ovided with a suitable device 170 to introduce`oil into the air stream. The ftunth` port. of the control` valve 166 isconnected Yto 'a pipe 171 for exhaust into the Vatmosphere. n

The 4-way control valve 166 is a two-position Valve of a well-known typethat is adapted for rotation 't`o its -two alternate positions by a pairof opposed lsoltenoids 172 and 173. When either of the two solenoids isenergized the control valve is rotated to the 'corresponding positionand remains in that posi'ti'on until the other solenoid' is energized.As shown in Figure 7`, the solenoid 172 is controlled by 'one of the two`foot switches 12m aad th jsoleiioiti 17s is @attenti by the other footswitch. Energi'zation of the solenoid 172'- places the pipe 1'64 incommunication with the hi'g'h pressure source and cnergizaton of thelsolenoid 173 places' pipe 165 in communication with the high pressuresource.

The manner in which the apparatus operates may be readily understoodfrom the foregoing description. The motor 104 is energized under thecontrol of a suitable switch (not shown) to drive thev belt Bcontinuously. With the tilt structure 21 inclined at the desired anglefor processing a work piece on the work supporting surface 22, theoperator anticipates the direction in which the tilt structure is to berotated for the next adjustment of the abrasive belt relative to theangle of the work supporting surface 22 and presses the correspendingyfoot switch of the pair of foot switehes 140. This switch action setsthe power cylinder 144 for the anticipated rotation of the tiltstructure by positioning the 4-wa`y control valve 166 torconnect one ofthe two ends of the power cylinder 144 with the source of compressedair. As a result, the compressed air in the power cylinder exerts forcetending to rock the operating arm 142 in the anticipated direction, butthe operating arm is prevented from responding to this' pressure becausethe by-pass valve 161 is closed to prevent movement of the piston in thehydraulic cylinder 150.

When the operator needs the anticipated change in inclination o'f thetilt structure 21, he merely presses his knee against the switch 141 toopen the by-pass valve` 161 to release theA hydraulic lock and thuspermit the power cylinder 144 to shift the operating arm 142. Themetering valve 162'in the bypass line 160 may be adjusted to regulatethe responsive movement of the operating arm 142 at whatever rate may bedesired. For accuracy, the rate should be relatively slow so that smallchanges in the tilt angle may be made with precision under the guidanceof the arcuate scale 39.

The apparatus is especially advantageous for the grinding of a surfaceo'n a work piece that progressively changes in angle relative to thework supporting snrface 22. For example, the work piece may be a flatmember having one longitudinal edge which is to change progressively inangle along the length of the work piece. To carry out the requiredgrinding operation, the operator divides the length of the workpieceinto small subdivisions, say, subdivisions approximately an inch or lessin length, and divides the over-all change in angle into incrementscorresponding to the subdivisions'. With such planning in advance, theoperator adjusts the tilt structure to the required initial angle andpresses one of the fo'ot switches 140 in accord with the anticipateddirection of change of the angle. The operator then grinds the firstsubdivision of the worl piece in accord with the initial setting of thetilt structure and then operates the knee switch 141 to swing the tiltstructure to the next angle under guidance of the scale 41 to carry outthe grinding operation over the next subdivision. Thus, with both handso`n the worli 8 pice, the operator is abley to 'carry 'out 'the grindingoperatn lpr't'ig'ressi'v'el'y arid accurately` 'from one 'end of theWork piece 'to another. The subdivisions may be as vsmall as necessaryto provide the progressive change in the langle of the ground surface ofthe work piece.

Since the wo'rlt supporting vsurface 2'2`e'xtend`s all around the tiltstructure 21, and since the tilt structure is of relatively lsinalldimensions in plan, the apparatus 'may be used to process work .piecesthat 'are relatively extensive in length and breadth and are irregularin shape. The described bearing assembly 'for pivotally supporting thetilt structure vmakes lit possible to provide such an extensive worksupporting surface free from obstacles y Whenever 'it is necessary Ytogain access to the interior of y"the vtilt structure, itK'is' a simplematter to remove the wall 'member 21 from the 'side 'of the shroud andto remove Vthe adjacent plate 'of the plurality of top plate 23. It is asin'i'ple matter, therefore, to` remove a worn abrasive belt and 'to'install' a 'replacement belt with minirnum loss of production time.

-The second 'embodiment of the invention shown in Figures '8 to 12comprises a base structure, designated as a whole by numeral V180, and atilt structure, designated as `a whole by numeral 1181, these twostructures being ofthe same general char'aeter as in the firstembodiment of 'the invention. The work supporting surface 182 of thebase structure is "formed by a plurality of top plates 183 supported byasu'table 'frame structure. The frame structure includes four heavytubular upright members 1186finter'c'onnected by upper'hrizontal ang-les1'87 and by lower fhrieiital. angles 188. At 'the rear end of the basestructurefan yauxiliarylfr'ar'r'it'work including tubular members189'and` angles 190 is provided to 'support certain components of theapparatus. Preferably the base structure ist) 'is 'meuntd on vsnortadjustable legs 191 as inthe nrst embodiment.

As best shown in Figure 9, the work supporting surfaee l 182immediately' 'in frdt'it of the tilt 'structure 1'81 is providedl by atwolplate 'member 192- that incorporates a p1uraiity'of'fewaporstr@einT93 to absorb heat from the. work supporting surface, The evaporatorCoils 193 are part of a conventional refrigeration system vwhichincludes a 1notor11`96, a compressor 197, a fan 1'98, and a condenser200'. A y l Hereaga'in the tilt structure 181 'includes a lheavy sideplate z jos which is Qnedside cia shi-oud having a front walrzoa, rearwan 20s, and a reinvabie sie@ wan member 206 4which 'is releasably Vheldin place by suitable fastening Adevices 207. To gain access totheinterio'r of 4thelshroud 'fry'the purpose of changing the abrasive lbelt,'B, 'it 4is. 'merely `necessary 'to remove the top plate 183@ (Figure"l`1*) 'adjacent thetilt structure and then tol remove thejside wanmember 206.

The tilt structure 181 may be lprovided 'with the usual meansto back upthe* abrasivel belt B adjacent the work supporting surface '182. As4best shown in Figure 9 suchrneans ymay comprise "alcasting 208 'insidethe shroud having a 'plate portion z`9 lpositioned in Contact with the'itiner'su'r'face of ythe `abrasive belt.

As best shown "ini Figure 9, the' work 'supporting surface 1782'ofltl`e"'ba`sestructure 181 terminates 'in a'beveled ed'ge2`f1'0close Etothe abrasive surface df the belt B andft'he tlt 'structure l:is adapted;to rotate about an axis that elselyapproximates the bevelededge 210; Thebelt By passes -ver'an upper idler pulley 2:11 and 'passes under a lowerdrive pulley j2`1'2' which preferably is encased byja rubber peripheralmember 21'3. The upper idler pulley yis mounted by suitableI bearings214 on a spindle 215 'and the spindle in turn is mounted on anadjustment plate 216. The adjustment plate 2146 has a laterallprojection 219 which extends through a slot 220 the Ytiltstr'ueture sideplate 203 and which is pivotallyeonnected toan outer slide bracket22i1`by a suitable pivot pin-222. .fvlhreadednrto the outer side`bracket 22-1 is an adjustment screw 22S carrying a lock nut 226.

The adjustment screw 225 extends through a lower slot 227 in the heavyplate 203 to bear against the adjustment plate 216. It is apparent thatadjustment of the screw 225 controls the angle of the adjustment plate216 about the axis of the pivot pin 222 and thus controls the angle ofthe axis of the idler pulley 211 relative to the tilt structure sideplate 203. The outer slide bracket 221 is slidingly retained by a pairof guide rails 228 for vertical movement to vary the spacing of theidler pulley 211 from the driven pulley 212.

A feature of this second embodiment of the invention is that the idlerpulley 211 is normally urged upward in a yielding manner to maintain thebelt under tension with manually operable means available to retract thepulley downward whenever it is necessary to replace the belt. To providethis feature, the outer slide bracket 221 is provided with an arm 231that extends inward through the slot 227 and carries at its inner endboth a dise 232 and a downwardly extending tube 233. Mounted on theinner face of the tilt structure side plate 203 is a bracket 234carrying a second disc 235 as well as an upwardly extending tube 236that slidingly telescopes into the first tube 233. The disc 235 isadjustable relative to the bracket 234 and for this purpose is mountedon the upper end of an adjustment screw 237, the screw being threadedinto the bracket and carrying a suitable lock nut 238. A suitablehelical spring 240 surrounds the two telescoped tubes 233 and 236 incompression between the two discs 232 and 235 to urge the outer slidebracket 221 upward. The pressure exerted by the spring may be varied byadjustment of the screw 237 carrying the lower disc 235.

Downward retraction of the idler pulley 211 against the opposition ofthe spring 240 may be accomplished by a cam 244` The cam is in the formof disc mounted eccentrically on a pivot pin 245, which pivot pin iscarried by a pair of ears 246 fixedly mounted on the shroud of the tiltstructure. A finger 247 extends upward from the outer slide bracket 221between the two ears 246 for co-operation with the cam 244. The cam 244carries a suitable operating lever 248 which is normally in the positionshown in Figures 10 and 11 with the cam 244 rotated upward away from thefinger 247. When the operating lever 243 is swung 180 clockwise from theposition shown in Figure l0, the cam 244 acting on the end of the finger247 depresses the outer slide bracket 221 against the opposition of thespring 240 to permit the belt B to be removed from the two pulleys forreplacement by a fresh belt.

The lower drive pulley 212 is carried by a shaft 250 that is journaledin a pair of bearings 251 in a cylindrical bearing member 252. Thebearing member 252 extends through the tilt structure side plate 203 andis attached thereto by suitable means including screws 253. Mounted onthe outer end of the shaft 250 is a sheave 254 which is operativelyconnected to a second sheave 255 by a multiple V-belt 256. The secondsheave 25'5 is on the shaft 260 of a motor 261 which motor is mounted bysuitable screws 262 to a base casting 263 on the exterior of the tiltstructure. Preferably the screws 262 extend through suitable slots (notshown) in the base casting to permit adjustment of the motor relative tothe base casting for the purpose of adjusting the tensioning of themultiple V-belt 256. Preferably the base casting 263 is formed with atleast one ear 264 through which extends corresponding adjustment screws265 bearing against the under side of the motor 261. It is apparent thatwith the screws 262 loosened the adjustment screw r screws 265 may bemanipulated to change the position of the motor 261. Preferably theadjustment screws 265 are provided with suitable lock nuts 266.

The tilt structure 181 is provided with the usual arcuate index member270 having a scale 271 thereon calibrated in terms of degrees. In thisembodiment of the invention the tilt structure also includes a hood orlamp housing. 272 incorporated in the shroud toaccommodate a lamp 273for illuminating the work surface in front of the belt B.

A further feature of this embodiment of the invention is the provisionof a blower system to carry away particles released by the abrasiveaction of the belt B.l For this purpose the lower closed end of theshroud that surrounds ythe belt is provided with a rearward extension274 which serves as a discharge chamber and is connected to one end of aflexible suction duct 275. The other end of the suction duct 275 isconnected to the intake 276 (Figure 1l) of a centrifugal blower 277. Byvirtue of this arrangement, a continuous stream of air enters a window278 in the shroud where the vbelt is exposed for its abrasive operationand the air stream sweeps downward through the shroud to draw. releasedparticles through the shroud. The circulation of air in this manner alsoserves the useful purpose of dissipating part of the heat generated bythe abrasive action of the belt.

The tilt structure 181 is pivotally mounted on the base structure bymeans of a trunnion member 282 and two spaced bearing members 283 and284. The trunnion member 282 is of the same construction as the trunnionmember 112 in the first embodiment of the invention and the two bearingmembers 283 and 284 are of the same construction as the correspondingbearing members 113 and 114 in the first embodiment. Thus, the trunnionmember 282 has a flange peripheral rib 285 corresponding to each of thetwo bearing members and each of the two bearing members is formed with agroove 286 of the required cross-sectional configuration for engagementwith the corresponding trunnion rib 285. Each of the two bearing members283 and 284 comprises two separable sections 287 interconnected bysuitable means including screws 288.

The outer bearing member 234 may be braced on two sides by threaded rods302. The upper ends of the two brace rods 302 are threaded into one ofthe top plates 183 and the lower ends extending through a horizontalangle 303 carry nuts 304 for engagement with the angle.

The inner bearing member 283 is mounted on a vertical plate 305 Which isbraced at its rear end by a transverse channel member 306. As best shownin Figure l0, a block 307 fxedly mounted on the vertical plate 305 atits lower edge may carry au adjustment screw 308. This adjustment screwexerts upward pressure on the inner bearing member 283 by means of aninterposed pressure plate 309. Preferably the adjustment screw 308carries a suitable lock nut 310. i

Preferably a lubrication system is provided for the described bearingarrangement. For this purpose the trunnion member 282 may be providedwith suitable bores 311 (Figure 12) associated with each of the twobearing members 283 and 284. The bores 311 are supplied withlubricant bya flexible tube 312 and communicate with the coacting bearing surfacesas shown.

The trunnion member 282, which may be attached to the tilt structureside plate 203 by a plurality of screws 314, is preferably reinforced bya pair of diagonal braces 315. The lower ends of the diagonal braces aremounted on the heavy side plate 203 of the tilt structure and the jupper ends are connected to the trunnion member 282 between the twobearing members 283 and 284.

In this second embodiment of the invention, the tilt structure 181 isrotated from one angle of inclination to another by means of a poweractuated pinion 316 in engagement with an arcuate rack 317 on the lowerend of the tilt structure. The pinion 316 is mounted on a shaft 318 thatextends from reduction gearing in a gear case 319. The reduction gearingin the gear case 319 is driven by a shaft 320 which is operativelyconnected to a second set of reduction gearing in a second gear case321. The operative connection between the two gear cases comprises twouniversal joints 325 and an f1 intermediate S'haff saffier; 326. Thereduction gearing in die se-Cananea case szri's cbanecd by a Shaft 327to a suitablemotor 328; It is apparent thatv energization of' He moresis'wiu attirare the pinion 31610 swing the tiltst'ructu're 251 and'thatthe rate of rotation of the tilt strueture will be desirably slow byvirtue of the two set'sfof reduction gearing. i

The direction of rotation of the motor 32'8 may be controlledby ar'evers'ing'switch 330 (Figure l'l) on the front o'f the ajjiparatus,`whieh reversing switch has an operating handle yor finger piece 331 thatis movable between two alternate positions. Energization of the motor328 may be controlled by a suitable knee switch 332. Preferablyanautomatic magnetic brake 333'is associated with the motor y328 in awell-known manner to lock the shaft 327 vagainst rotation automaticallywhenever the m'tr sis'rs (1e-energized.

It will be 'apparent that the second embodiment of the invention vw'illoperate in thesame general manner as the first described embodiment.

My Adescription of the two embodiments in specific detilby wayof'di'sclosure and to illustrate the principles involved'will suggest tothose skilled in the art various changs, modi'cations and'otherdepartures from my disclosure that properly fall within the spirit andscope of the appended claims.

1. A grinder ofthe character described having in combination: a basestructure having a work supporting surface; an abrasive belt; a tiltstructure to support said belt for movement' of the belt'longitudinallyalong an operatingpath intersecting the plane of said work supportingsurface; .and means pivotally supporting said tilt structure on saidbase structure for adjustment rotation about a fixed axis substantiallycoincident with the intersection of said operatingpath and the plane ofsaid work supporting surface, so that all the directions of adjustmentof saidA path radiate from substantially a single line on the plane ofsaid work supportingv surface to minimize the bodily shifty of akworkpiece required to maintain contact'by the workpiece with said beltduring wide changes in angle of the belt relative to thework supportingsur-v face.

-2. A combination as set forth in claim 1 in which said pivotalsupporting means comprises a bearing assembly that is a segment ofacircle in cross-section and lies entirely below the plane of said worksupporting surface to avoid interference with work pieces on saidworksupporting surface.

3. A combination `as set forth in claim l in which said work supportingsurface of vthe base structure terminates in a straight edge adjacent toand parallel to said belt and in which said axis of rotationapproximately coincides with said straight edge.

4 A grinder of the character described', having in combination: a basestructure having a work supporting surface; an abrasive belt; a tiltstructure to support said belt for movement of the belt longitudinallyalong an operative path intersecting the plane of said work supportingsurface; and means including a trunnion member extending laterally fromsaid tilt structure and a cooperating bearing member on said basestructure for pivotally supporting said tilt structure on said basestructure for rotationl about a fixed axis in the region of theintersection of said operating path and the plane of said worksupporting surface,said two members having a crosssectionalconfiguration of a segment of not more than half of a circle, said twomembers having cooperating arcuate shoulders to keep the trunnionmemberfseated in thebearing member'.

5. A combination as set forth in claim 4 in which the segmentalconfiguration of thetrunnion member is truncated for spacing of theltrunnion member away from said axis. 4 l v 6. A grinder of thecharacter described having in com- 12 bination: a base structure havinga work supporting surface for the support Vof work pieces; an abrasivebelt; a tilt structure to support said belt for movement of the beltlongitudinally along an operating path intersecting the plane of saidwork supportingsur'f'ace; means pivotally supporting said Vtiltstructure o'n said base structure for rotation of the tilt structure tovary the angle of said operating path relative 'to saidv work supportingsurface and cooling means mounted on said base structure to absorb heatfromsaid work supporting surface in the region adjacent saidoperatingpath of the belt.

7. A grinder asset forth in claim 6 in which said cool ingl meanscomprises a refrigeration system having an evaporator associatedwith-said work supporting surface.

8. A grinder ofthe character described in combination: abase structurehaving a work supporting surface for ther-support of a work piece; anabrasive belt; a tilt structure; Vpulleys on said tilt structure tosupport said belt Afor movement of the belt longitudinally along anoperating path intersecting the plane of said work supporting surface;means on said tilt structure to drive said belt; means pivotallysupporting said tilt structure on said base structure for rotation abouta fixed axis located substantially at the intersection of said operatingpath and the planeof said work supporting surface; and power means toadjust said tilt structure about said axis.

v9; A grinder as set forth in claim 8 which includes brake means ltoholdsaid tilt structure at different angles of adjustment relative tosaid work supporting surface.

l0. A grinder as set forth in claim 8 which includes remote controlmeans for said power means, said remote control means being adapted forresponse to movement of the leg of theV operator while the operators twohands are'engaged in holding a work piece on said work supportingsurface.

11. A grinder as set forth in claim l0 which includes a reversingcontrol for said power means adapted to be set-for either of twodirections of tilt adjustment.

12. A grinder as set'forth in claim 11 in which said remote controlmeans is a switch adapted to be operated by contact by the knee of theoperator.

13. A grinder as set forth in claim 8 in which said work supportingsurface terminates in a straight edge closely adjacent to the abrasivesurface of said belt and which includes cooling means to absorb heatfrom said work-supporting surface in the region adjacent said edge.

14. A grinder as set forth in claim 8 which includes means toexertforc'e on one of Asaid pulleys to maintain said belt-in tension andwhich includes manually operable means to relieve said tension to permitthe belt to be removed and replaced.

1'5. A grinder of the character described having in combination: a basestructure having a Work supporting surface to support a work piece, saidwork supporting surface terminating in a straight edge; an abrasivebelt; a Atilt structureadapted to support said belt for movement of thebelt longitudinally along an oper'ating path intersecting the plane ofsaid work supporting surface close` to said straight edge; meansA onsaid 'tilt structure toy drive said belt; means pivotally supportingsaid tilt structure on said base lstructure for rotation about an axisin the region of said straight edge to varythe angle of said operatingpath relative to the plane of 4saidwork supporting surface;refrigeration means including'an evaporator to absorb heat from saidwork supporting surface in the region adjacent said ystraight edge; atrunnion member extending laterally from one yside of said tiltstructure; at least one bearing member carried byl said base structureto journal said trunnion member, said two members each having thecross-sectional' configuration lof segment of a circle not greater thanhalf of the circle with the trunnion member and the bearingkrnemberbelow the plane of said worksupporting-*surface to avoidinterference with work pieces thereon; power means to rotate said tiltstructure to different angles relative to -sad base structure; means toindicate the angle of said tilt structure relative to said basestructure; and a remote control for said power means.

16. A grinder as set forth in claim 15 which includes a shroud on saidtilt structure to conine particles released by abrasion and whichincludes a blower on said base structure connected with said shroud by aexible duct to create an air stream to carry said released particlesaway from said work supporting surface.

References Cited in the file of this patent UNITED STATES PATENTS165,762 Sawyer July 20, 1875 859,466 Silvis et al. July 9, 1.907

Gough Dec. 22, 1903 15 14 Arburn Sept. 10, 1907 Bengler Sept. 14, 1915Brown Ian. 11, 1921 Hitchcock Mar. 31, 1931 Curtis et al Sept. 25, 1934Sassen Feb. 16, 1937 Tautz Feb. 18, 1941 Bostwick et al Nov. 3, 1942Bladenhofer Mar. 5, 1946 Spetz June 4, 1946 Bell July 31, 1951 Riedeselet al Oct. 30, 1951 McEwan June 2, 1953 FOREIGN PATENTS Great BritainDec. 20, 1950

